This invention relates to masonry structures in general, and more particularly to a technique for reinforcing existing masonry structures to provide greater structural strength and resistance to externally applied forces.
Known masonry structures typically comprise a series of rows of individual masonry elements, such as cement blocks, bricks and the like, adhered together using cementitious mortar or some other adhesive material. Both the mortar and the masonry elements exhibit inferior response to shear forces imposed on a masonry structure by external forces, such as winds and earthquakes, when compared to steel reinforced building structures. In addition, over time, the mortar deteriorates due to weathering, aging and other factors. As a result, the mortar loses adhesive strength, becomes soft and friable, thereby weakening the adhesive bond between the individual masonry elements. This further impairs the ability of such structures to withstand externally applied forces.
While efforts have been made in the past to reinforce existing mortar and masonry structures by using steel members, such as rods or beams, as part of a retrofitting operation, such efforts have been found to be either unreasonably expensive, incapable of retrofitting installation, incompatible with existing structures, relatively ineffective or a combination of these factors.
U.S. Pat. No. 4,694,621 for xe2x80x9cModular Building Constructing Meansxe2x80x9d issued Sep. 22, 1987, discloses a system for constructing modular metal buildings using a unique conical connector and fastening rods for connecting together the structural modules of a steel building. The unique conical connector is used in conjunction with a socket assembly rigidly secured to the building and a vertically oriented tensioning mechanism which passes through a bore in the connector in order to enable compressive/tensile force to be created in the vertical direction. A series of connectors, sockets and tensioning mechanisms are arranged in a vertical column from the foundation to the top of the building, and a plurality of such series of elements is provided in parallel columns distributed about and through the building. The system disclosed and claimed in the ""621 patent, while effective, was designed expressly for use in steel building construction. The disclosure of U.S. Pat. No. 4,694,621 is hereby incorporated by reference.
The invention comprises a method, structure and apparatus for providing an improved masonry structure which is relatively inexpensive to install, compatible with both new and existing structures, highly effective in strengthening a masonry structure and employs some of the principles and elements of the ""621 system modified and adapted to the specific requirements of masonry structures.
From a process standpoint, the invention comprises a method of providing a masonry structure with improved response to externally applied forces, the method including the steps of forming internal holes in the masonry walls from the top of a given wall to the foundation, installing a plurality of tensioning rod connector assemblies in the holes, with the bottom of each tensioning rod connector assembly anchored to the foundation, and post-tensioning the rods at the roof so that each rod connector assembly applies an axial load in compression to the wall in order to improve strength, performance and durability of the structure. In areas of the wall in which it is impossible or impractical to install a tension rod connector assembly, such as in window areas of a wall, additional spring-tension connector assemblies are installed to provide continuity at the floor diaphragm.
The holes are formed in the masonry walls using wet or dry core drilling techniques and procedures are followed for controlling and collecting the dust and debris caused by the core drilling to minimize environmental contamination. After formation of the holes, the holes are cleaned of residual dust and debris.
Both the tensioning rod connector assemblies and the spring-tension connector assemblies are installed by coupling a first portion of each connector assembly to the associated floor and coupling a second portion to the adjacent wall structure. Each type of connector assembly is also preferably installed by forming a void in the masonry wall structure at each desired location, installing a lower portion of the connector assembly in the void, filling a lower portion of each void with a hardenable liquid and permitting the liquid to harden, isolating the hardened liquid from the upper portion of each void, installing the remaining connector components, filling the upper portion of each void with a hardenable liquid and permitting the liquid to harden.
For masonry wall structures having a plurality of floors, the tensioning rod connector assemblies are installed progressively from the lowermost floor to the uppermost floor.
From a system standpoint, the invention comprises a system for reinforcing a masonry wall structure having a top, a bottom, and at least one floor intermediate the top and bottom, the system including a plurality of bores formed in the masonry wall structure between the top and bottom of the masonry wall structure; a plurality of series-connected post-tension rods and force transmission connectors located in each of the bores with the force transmission connectors located at the level of the at least one floor. The force transmission connectors each include a first portion coupled to the associated floor and a second portion coupled to the adjacent masonry wall structure. A plurality of spring-tension connectors are located in regions of the wall structure between the bores at the level of the at least one floor. Each spring-tension connector includes a first portion coupled to the associated floor, a second portion coupled to the adjacent masonry wall structure, and a tensioned spring coupled between the first and second portions to dampen relative motion therebetween.
A plurality of voids are formed in the masonry wall structure at the location of each of the plurality of force transmission connectors and spring-tension connectors. Each void contains an associated one of the connectors and has a first mass of hardened material in a lower void portion, a second mass of hardened material in an upper void portion, and a void separator located between the first and second masses.
The first and second portions of each of the connectors preferably includes a tapered wall portion, and each connector also preferably includes a connector member having a pair of tapered wall sections each received in a different one of the tapered wall portions of the first and second connector portions and a central through-bore for slidably receiving an associated one of the rods. At least one of the tapered wall portions is preferably coated with a low friction material.
The first and second portions of each spring-tension connector likewise includes a tapered wall portion, and each spring-tension connector also preferably includes a connector member having a pair of tapered wall sections each received in a different one of the tapered wall portions of the first and second portions of the spring-tension connector and a central through-bore. In addition, a fastener is received within the central through-bore for coupling the tension spring means between the first and second connector portions.
From an additional process standpoint applicable to structures with deteriorated mortar, the invention comprises a method of providing a reinforced masonry structure having individual masonry elements adhered together by an adhesive material, the method including the steps of removing the interstitial adhesive material between at least some masonry elements to a desired depth in order to form voids, forming bore holes in the adhesive material remaining in the voids at a desired spacing and to a desired depth, inserting an adhesive substance, preferably epoxy adhesive, into the bore holes, providing a plurality of reinforcing members each having a body portion and at least one leg portion extending away from the body portion, installing the reinforcing members into the voids by inserting the leg portions into the bore holes with the body portion of adjacent reinforcing members in mutual contact, inserting an adhesive substance, preferably epoxy resin, into the voids to cover the reinforcing members, and allowing the adhesive substances to harden so that the reinforcing members are secured to the masonry elements and to each other.
The body portions of the reinforcing members preferably terminate at one end in an offset end section, and the step of installing the reinforcing members into the voids preferably includes the steps of aligning the offset end section of each reinforcing member with the end of the adjacent reinforcing member in order to form a lap joint.
The method also preferably includes the additional step of applying a finishing adhesive coat over the adhesive substance in the voids in order to match the original color and texture of the adhesive material to retain the original visual appearance of the masonry structure.
From an additional combination standpoint, the invention comprises a reinforced masonry wall structure having a plurality of masonry elements adhered together in row and column fashion by an adhesive material, usually mortar, a plurality of spaced bore holes formed in the mortar to a desired depth, a plurality of reinforcing members each having a body portion and at least one leg portion extending away from the body portion, the leg portions of each reinforcing member being received within an associated bore hole, a first adhesive substance received in the bore holes, adjacent ones of the plurality of reinforcing members being in mutual contact, and a second adhesive substance formed over the plurality of reinforcing members to bond the reinforcing members to the masonry elements and to each other. The first and second adhesive substances are preferably epoxy adhesives.
The body portion of each of the plurality of reinforcing members preferably has an offset end section and a second end section, and the offset end section of each reinforcing member is preferably aligned with the second end section of an adjacent reinforcing member to form a lap joint. The reinforcing members are preferably fabricated from metal wire.
Each reinforcing member preferably has a plurality of pairs of leg portions spaced along the body portion, each pair comprising a U-shaped segment secured to the body portion.
From an additional component standpoint, the invention comprises a reinforcing member for use in forming a reinforced masonry structure with a plurality of masonry elements adhered together by an adhesive material, the reinforcing member comprising an elongate body having a longitudinal axis and at least one leg portion extending away from the longitudinal axis and adapted to be received within bore holes formed in the adhesive material and bonded therein by means of an adhesive substance. The elongate body terminates in a first end section adapted to engage the end of an adjacent reinforcing member when installed in the masonry structure in order to provide mutual contact therebetween.
The first end section of the reinforcing member is preferably offset from the longitudinal axis so that a lap joint is formed between the first end section and the end of an adjacent reinforcing member during installation.
The reinforcing member preferably has a plurality of pairs of leg portions spaced along the elongate body, with each pair comprising a U-shaped segment joined to the elongate body.
Each member is preferably fabricated from metal wire, notably steel, and each U-shaped segment is preferably joined to the elongate body by welding.
For a fuller understanding of the nature and advantages of the invention, reference should be made to the ensuing detailed description taken in conjunction with the accompanying drawings.